1. Field of the Invention
This invention relates to binary code reading and decoding devices and systems, and particularly to a reader for accurately decoding magnetically recorded binary codes at varying reading speeds.
2. General Description of the Prior Art
Magnetic recordation of digital information on credit cards has increased enormously in the past few years. With this increase, there has occurred a substantial increase in the demand for readers for such recordings, particularly for retail and banking establishments. Such a reader must decode the particular magnetic code employed, and as an example, FIG. 3a illustrates perhaps the widest used code, the Aiken self-clocking code. As shown, it typically employs an initial set of 8 to 10 magnetically encoded "0's", each having a physical length on the card of 13 1/3 mills, and after which there follows binary encoded data wherein "0's" are the indicated length "L", and "1's" are a pair of lengths half this length, each 6 2/3 mills. In order to effect reading of a card, the card must be moved through the reader with a magnetic head or heads of the reader in engagement with the magnetic track of the card, and this is accomplished on some readers by means of an automatic transporter; and on other readers it is simply performed by moving the card through the reader by hand. Where done automatically, the speed of movement of the card is of a constant and known speed, and thus the different length encoded pulses may be time-base detected, minimizing the electronic circuitry problem. On the other hand, the machanical hardware required adds complexity to the reader, and this in turn makes it somewhat costly and maintenance prone. Hand-operated devices on the other hand have heretofore required more complex electronic systems in order to detect different inter-flux reversal times without some reference, such as speed of movement of a card. One such system employs an electronic clock and two counters, and clock pulses are counted for each succeeding period between flux reversals. By comparison of succeeding counts, different time periods between magnetically encoded pulses may be discriminated and thus decoded. The difficulty with this system is that because of the extremely wide speed variations in hand transported cards (1.5 to 40 inches per second), quite high clock pulse rates and many stages in the dual counters are necessary to achieve accuracy, so this has resulted in a fairly high cost for this type of system. A proposed system, which the applicant earlier implemented and discarded because of cost, utilized a compound head equivalent to two reading transducers, both placed upon the track to be decoded, but slightly displaced along the track. Length domain decoding was then accomplished by various auto-correlation methods using these two length displaced signals.
Another problem with the present systems is that of mechanically coping with deformed cards and providing an apparatus which reliably maintains the card in contact with the reading head of the reader during the transport of the card through the reader. The conventional approach is to provide a floating spring biased guide or wheel which urges a credit card into continuous contact with the head. The difficulty with this approach has been wear of moving parts and guide surfaces that scour the card's signature area. It is clear that reliability could be significantly improved if spring arrangements and moving parts in general could be reduced or eliminated.
Accordingly, it is the object of this invention to provide an improved reading-decoding system which is both mechanically and electronically simpler than that which now exists and which can be fabricated at a significantly lower cost.